1. Field of the Invention
The present invention relates to selection of a relay device that actually relays content data from among a plurality of relay devices that can relay content data transmitted among a plurality of transmission terminals.
2. Description of the Related Art
Television conference systems that conduct, for example, a television conference via a communication network, such as the Internet, are known as an example of a transmission system that transmits and receives content data to and from a plurality of transmission terminals via relay devices. In response to a recent trend toward reduction in expenses and time spent in business trips, there is a mounting need for such television conference systems. Such a television conference system typically includes a plurality of television conference terminals as exemplary transmission terminals. A television conference can be achieved by such television conference terminals that transmit and receive image data and sound data among themselves.
Recent efforts made toward enhancing a broadband environment have made possible transmission and reception of high-quality image data and high-sound-quality sound data. The condition of the remote end of the television conference can thus be more readily determined, so that the quality of communication through conversations has been improved.
When, for example, a large number of television conferences are conducted via the communication network or image data or sound data is received through a narrow-band path on the communication network, however, a delay occurs in reception of the image data or the sound data. When a delay of 0.5 seconds or longer occurs in the reception of the image data or the sound data, television conference system users are likely to feel stressed during conversations. As a result, the users are still not satisfied with the television conferences conducted in the recent enhanced broadband environment.
Additionally, recent television conference systems include a relay device that relays image data and sound data among the television conference terminals, for each local area network (LAN) in the communication network. Communication processing in a television conference can be distributed among these relay devices, so that load on each relay device can be reduced and the volume of image data and sound data to be relayed can be distributed.
Conventionally, a relay device connected to a LAN to which a television conference terminal that conducts a television conference is connected has been selected from among a plurality of relay devices. Specifically, a relay device having an IP address close to the IP address of the television conference terminal is selected to transmit and receive therethrough image data having high image quality, for example (see patent document 1 (Japanese Patent Application Laid-open No. 2008-227577)).
Communications for television conferences, for example, are performed not only within the same prefecture, but also over long distances in Japan, such as between Hokkaido and Okinawa, and across different countries, such as between Japan and the U.S.
Thus, when a relay device close to a first transmission terminal, such as a television conference terminal, is selected, the selected relay device is far away from a second transmission terminal, so that well-balanced high-quality content data cannot be transmitted or received under an actual communication network environment.